The present invention relates to a process and apparatus for coating a material length, especially a textile material length, e.g. a tufted carpet, or a plush of natural or synthetic fibers, with a fluid coating substance, e.g. a dyeing liquor. The present invention is also directed to an apparatus for heat-setting and possibly bonding the substance applied.
Apparatus for the continuous coating and further processing of wide lengths of bulky textile materials, e.g. wool and polyamide fibers are well known. In these well known devices the textile materials are submitted to the following consecutive process stages:
1. Application of dyestuffs and auxiliary agents, e.g. by means of a padding or printing unit;
2. A HEAT-TREATMENT STAGE, PREFERABLY WITH SATURATED STEAM, FOR FIXING THE DYESTUFFS, ESPECIALLY WITH MATERIAL PENETRATION DURING THE HEATING-UP PROCESS;
3. A WASHING AND RINSING PROCESS, PREFERABLY WITH MATERIAL PENETRATION; AND
4. A HEAT-TREATMENT PROCESS, ESPECIALLY A HOT AIR TREATMENT FOR DRYING, PREFERABLY ON AT LEAST ONE SIEVE DRUM SUBJECTED TO A SUCTION DRAFT.
The well known devices are thus principally suited for dyeing and possibly for dyeing and bonding needled felt carpets of any fiber on which the dyestuffs are fixed in a saturated steam atmosphere. However, tufted carpets and other pile material lengths are inadequately dyed on these devices, since pile materials should not be squeezed after the dyestuff application in order to avoid a deformation of the pile. Applicators without subsequent squeezing, which are known up to now, contain many substantial disadvantages. A uniform application over large working widths and an exact metering of the required dyestuff quantities as well as a good dye penetration down to the carpet base are accomplished with great difficulty.
One device for coating a material length with a fluid coating substance is already well known. This device comprises a trough filled with liquid and an overflow edge over which part of the liquor flows into a collecting container. A roller partly immerses in the liquor. The material to be coated is guided over this roller and while passing through the liquor it is wetted. Behind the liquor trough is arranged a doctor operating with air and a stationary stripper which removes part of the liquor adhering to the material length. Such a device can be used for coating, e.g. with a bonding agent or a synthetic resin dispersion. However, it is difficult to apply a dyeing liquor with such a device, since because of the dye affinity of the material to be coated, e.g. the tufted carpet made of a polyamide, the liquor which is stripped from the material contains less dyestuffs than originally. An accurate addition of a corresponding amount of dyestuffs to this liquor is extremely difficult and time-consuming. However, in a continuous operation it is imperative that exactly the same shade is obtained over many treatment hours.
In order to avoid this reduction of the dyestuff content in the dyeing liquor, a device has already been suggested wherein the dyeing liquor is poured onto the material. Such a well known device again comprises a trough in which the fluid coating substance is contained. A roller immerses into the trough and carries along part of the fluid coating substance. To the roller a doctor is correlated with which the dyeing liquor is removed from the rotating roller and passed on to the material to be coated. With such a device it is possible to apply a uniform dye film, e.g. over large widths of 5 m and more, to the material to be coated, e.g. a tufted carpet. However, this device incorporates the disadvantage that the thickness of this dye film is substantially influenced by the viscosity of the fluid coating material (the dyeing liquor) and that a certain thickness cannot be exceeded, even at high speeds of the roller.
Since, particularly in differential dyeing processes, large dye-stuff quantities of up to about 400 to 500% and more, based on the material weight, are to be applied, such a coating device does not meet present needs. (Carpet lengths have generally a weight of 800 g/m.sup.2 to 1600 g/m.sup.2.) Up to now, the remedy which has been found is that several of such coating devices are arranged one behind the other and a film of the coating substance is poured onto the material several times. Of course, the use of several such coating devices is expensive.